How to change a Decaster coordinate to Polar coordinat plot

Hello everyone. I want to change plot from Descartes coordinate (code) to polar coordinate,

grid_num1=72;                 % system matrix size
grid_num2=46;                % system matrix size

yn=xlsread('source position.xlsx');                  % input file
sys=xlsread('system matrix.xlsx');           % system matrix
iteration_num=5000;                          % iternation number

yn_1=[yn(1:180,:);yn(1:180,:)];
sys_1=[sys(1:180,:);sys(1:180,:)];

tic
figure;    
lamda=ones(grid_num1*grid_num2,1);
I=ones(360,1);
cal=sys_1'*I;   
iii3=0;

pre_lamda=0.01*ones(grid_num1*grid_num2,1);
iii=0;
output_image=zeros(grid_num1,grid_num2,iteration_num);

tic
while(iii3<iteration_num)
    A_lamda=sys_1*lamda;
    lamda=lamda.*(sys_1'*(yn_1./(A_lamda)))./(cal);
    iii3=iii3+1;
    output_image(:,:,iii3)=reshape(lamda,[grid_num1 grid_num2]);
end
time=toc;

reshape_lamda=reshape(lamda,[grid_num2 grid_num1]);
xx=[0 360];
yy=[0 90];
imagesc(xx,yy,reshape_lamda);
title(['Reconstructed Image Using MLEM'])
xlabel('Phi [degree]')
ylabel('Rho [degree]')
colormap hot
colorbar;
toc

Descartes plot:

Polar plot that I expect: In Polar plot, I want to see 2 white rectangles in Descartes plot.

Thank for your time